1. Field of the Invention
This invention relates generally to an engine cover mounted on internal combustion engines of automobiles or the like, and more particularly to such an engine cover including a rigid cover body made from a resin or metal and covering an engine, and a foamed member fixed to an inner face of the cover body.
2. Description of the Related Art
JP-A-2002-28934 discloses one of conventional engine covers of the above-described type. The disclosed engine cover comprises a cover body made of a resin or metal and a foamed member fixed to a back side or inner face of the cover body. The foamed member has a configuration conforming to an outer surface of the engine and is pressed onto the outer surface of the engine. However, the above-described conventional engine cover cannot achieve a sufficient sound reduction.
Therefore, an object of the present invention is to provide an engine cover which can effectively reduce sound produced by the engine.
The present invention provides an engine cover comprising a rigid cover body made of a resin or metal and covering an engine, a foamed member fixed to an inner face of the cover body and including at least a part thereof spaced from the engine, and a plurality of corrugations formed on the part of the foamed member spaced from the engine.
A sound-absorbing area of the engine cover is increased with increase in a surface area of the foamed member since the foamed member is formed with a plurality of corrugations. Consequently, sound produced by the engine can effectively be reduced. Further, since a part of the foamed member is spaced from the engine, a space is defined between the foamed member and the engine. Consequently, sound produced by the engine can be damped by air in the space.
In a preferred form, the corrugations are disposed on an inner face of the expanded portion so that the space is defined between the foamed member and the engine.
In another preferred form, a difference between a ridge of each protrusion and a trough between said each protrusion and the adjacent protrusion is set at a quarter of a wavelength of the predetermined sound, the quarter being multiplied by any integer. The predetermined sound interferes with sound reflected on the corrugations thereby to deny each other. Consequently, the predetermined sound can effectively be reduced.
In further another preferred form, the engine cover includes a wall standing from an edge of the foamed member so as to extend toward the engine. Since the sound-leakage preventing wall restrains sound produced by the engine from leaking outside the foamed member, the sound produced by the engine can effectively be reduced.
Additionally, in further another preferred form, the cover body includes a rib projecting toward the engine from a peripheral edge of the expanded portion on an inner face thereof. The rib can improve the rigidity of the cover body. The improvement in the rigidity of the cover body can restrain the engine cover from vibrating due to vibration produced by the engine.